U.S. Statutory Invention Registrations (SIR) H202 and H342 by Geeter entitled "Barrel Flexure Control System" & "Apparatus to Improve Accuracy of guns Through Barrel Flexure" both teach of gun barrel moment generating components in combination with either an open-loop or very crude closed-loop control devices for control of a gun's barrel flexure. The (SIR) H202 teaches of two actuator elements in quadrature with fluidic piston control device attached to the gun barrel at a fulcrum position that additionally includes linear voltage differential transformers for positional feedback signals for control of these actuators. The (SIR) H342 teaches of the same two actuator elements with fluidic piston control attached at a fulcrum position of the gun barrel with an additional feature components that direct the flow of hot gases from the gun barrel for controlling barrel flexure. The SIR H342 is a continuation-in-part of Geeter's earlier SIR H202 with more information regarding the earlier device's performance and that the actuators used for barrel flexure can be either electrical, mechanical in construction.
Limitations of these two SIRs compared with the instant invention include Geeter's use of a bearing based structural member for attachment of the fulcrum members to a gun barrel with actuators that act directly on the gun barrel. The instant invention uses actuators that act on the bracket members rigidly attached to a gun barrel. This feature allows for better flexure controllability with greater bandwidth capability since the instant invention's bracket design is more rigid for a given mass for various calibered guns along with being lighter and more compact. This factor is significant when designing large diameter barrels since bending large diameter gun barrels requires comparable large forces. The outer cylindrical protective structure of Geeter's flexure control assembly would be much larger and heavier for a required rigidity to enable efficient transfer of energy from the actuator to the barrel. Next, an increase in the gun barrel's actuator capacity using the instant invention requires comparatively less of an increase in the supporting bracket's size to satisfy geometrical and durability design constraints. Finally, Geeter's devices do not use muzzle sensory feedback for controlling the actuators in combination with a gun turret control as in the instant invention.
Geeter's preferred open-loop control scheme of actuator commands is determined using standard calibration tests performed by ten shots fired from a candidate gun system where the impact location of each shot is measured. Using these data, a standard mean barrel bending actuator command is determined to counteract the muzzle's motion for minimizing distance between a projectile impact and the point of aim for each shot fired. These averaged commands are used to drive the bending actuator whenever the gun is fired. Geeter's design provides no measurement of a muzzle's deflection during gun firing as required by the instant invention for more accurate firing of the gun. Next, Geeter's preferred open-loop control scheme is very problematic since: i) the actuator command signals are determined experimentally based on a series of test firings and ii) there is no sensory feedback of muzzle displacement which inherently makes the gun sensitive to variations in physical parameters in which it operates. These parameters include: barrel temperature, differences in ammunition used from one round to the next, number of rounds fired in a short duration, gun orientation and actual physical condition of the gun system. In contrast, the instant invention described herein uses feedback control to directly measure and regulate the muzzle orientation resulting in precise directional control of an exiting projectile. Also, when using closed-loop muzzle deflection feedback control, compensation can be built into the device for variations as described above.
The instant invention's gun barrel flexure actuator assembly additionally compensates for i) barrel droop, ii) barrel whip and iii) platform motions. These three phenomenon effects are minimized by the invention's muzzle sensory feedback subsystem, a feature not taught or suggested by the Geeter's devices. In particular, barrel droop is a physical phenomenon occurring in long gun barrel systems such as tanks and artillery pieces that deflect significantly in response to increased gun barrel temperature caused by either repeated gun firing or exposure to intense sunlight. Barrel whip is a phenomenon in which the barrel muzzle displaces or whips violently as the projectile travels inside the barrel from the breach towards the muzzle. Both of these physical phenomenon cannot be compensated for since there is no feedback element in Geeter's muzzle design. Finally, Geeter's invention cannot compensate for the affects of platform motion on muzzle displacement. Geeter's open-loop control scheme is calibrated upon firing groups of 10 test rounds and measuring the distances of each round from the aim point assuming a rigid base. If a gun's mounting base experiences random motion, Geeter's calibration data are incorrect and the accuracy of the gun is suspect. Accordingly, the present invention is an improvement over the current state of the art in barrel flexure techniques for accurate aim and targeting of a projectile.